<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .box {
        position: relative;
        width: 400px;
        border-bottom: 1px solid #ccc;
        margin: 100px auto;
    }
    
    .box input {
        width: 370px;
        height: 30px;
        border: 0;
        outline: none;
    }
    
    .box img {
        position: absolute;
        top: 6px;
        right: 5px;
        width: 24px;
    }
</style>

<body>
    <div class="box">
        <label for="">
            <img src="images/小眼睛2.jpg" alt="" id="eye">
        </label>
        <input type="password" name="" id="pwd">
    </div>
    <script>
        var eye = document.getElementById('eye');
        var pwd = document.getElementById('pwd');
        var flag = 0;
        eye.onclick = function() {
            if (flag == 0) {
                eye.src = "images/小眼睛1.jpg";
                pwd.type = 'text';
                flag = 1;
            } else {
                eye.src = "images/小眼睛2.jpg";
                pwd.type = 'password';
                flag = 0;
            }

        }
    </script>
</body>

</html>